EMC2302 datasheet(42/44 Pages) SMSC

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Dual RPM-Based PWM Fan Controller

Datasheet

Revision 1.1 (10-12-09)

SMSC EMC2302

DATASHEET

PWM Frequency vs. Ambient Temperature

DD = 3.3V, Base Frequncy = 26Khz

25000

25200

25400

25600

25800

26000

26200

26400

26600

26800

27000

-50

100

150

T emp er at ur e ( C )

Ambient Temperature (°C)

PWM Frequency vs. Supply Voltage

TA = 25C, Base Frequncy = 26Khz

25000

25200

25400

25600

25800

26000

26200

26400

26600

26800

27000

2.95

3.05

3.15

3.25

3.35

3.45

3.55

3.65

Supply Voltage (V)

PWM

Output

10x

Zoom on

PWM

Output

Spin Time = 1.0s; Spin Level = 55%; Updated Time = 200ms;

RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm Spin Up Routine

t = 0

Duty Cycle Measured = 53.8%

PWM

Output

10x

Zoom on

PWM

Output

Spin Time = 1.0s; Spin Level = 50%; UpdateTime = 200ms;

RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm Spin Up Routine – NoKick

t = 0

Duty Cycle Measured = 50%

PWM

Output

10x

Zoom on

PWM

Output

Update Time = 200ms; Max Step = 16 PWM counts

RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm PWM Ramping

Spin Up Routine Ends – begins normal

operation

Update Time ends, PWM duty cycle changed

Update Time ends, PWM duty

cycle changed

Duty Cycle

Measured

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